1. Field of the Invention
The invention relates to an air-conditioning installation, in particular for motor vehicles.
2. Related Art of the Invention
An air-conditioning installation of the generic type is known from DE 37 04 182 A1. In that installation, a cooling installation is operated in combination with a refrigeration accumulator, with the refrigerant being used as heat-transfer medium to transfer the refrigeration from the refrigeration accumulator to the evaporator with the aid of a circulation pump. Evaporator and refrigeration accumulator are connected in parallel on the refrigerant side, which leads to high levels of outlay on connections and components and therefore disadvantageously to high manufacturing costs. Furthermore, an installation of this type of course also takes up valuable space in a motor vehicle, in particular in a passenger automobile.
Conventional refrigeration systems in vehicles are generally driven by a refrigerant compressor only, which is fixedly connected to the vehicle engine via a belt drive. If the engine is not operating, neither is the air-conditioning installation. The passenger compartment can heat up very quickly in summer. The consequence of this is that drivers leave the engine running even in traffic jams or during periods of waiting, in order to keep the air-conditioning installation operating. This is a practice which is a considerable burden on the environment, on account of pollutant and noise emissions, and in addition consumes fuel.
In the case of vehicles with a start/stop function, the engine is automatically switched off as soon as the vehicle is stationary (even in the event of relatively short stops, for example at a red traffic light), in order to reduce fuel consumption. Consequently, the refrigeration installation likewise stops, and consequently it is impossible for functions which are of relevance to safety and comfort, such as cooling and drying of the incoming air for the passenger compartment, to be performed.
Stationary air-conditioning systems have already entered series production in the field of commercial vehicles. This is a standard which is far from being reached in the air-conditioning of passenger automobiles. The current concepts are as yet unsuitable for use in passenger automobiles, on account of the ratios of performance to space and weight.
Stationary air-conditioning concepts with generally indirectly loaded storage evaporators, which have poor cooling dynamics and only effect cooling immediately after the engine has stopped, are known in practical applications.
Furthermore, electrically driven compressors are known, for example in combination with belt-driven starter generator, integrated starter generator or as a hybrid compressor, i.e. as a compressor with integrated electric motor. However, this disadvantageously requires larger batteries and generators. The vehicle then has a high energy consumption when it is stationary. Moreover, the efficiency is very poor on account of the very long chain of action (generator/battery/refrigerant compressor).
Refrigeration installations with a secondary coolant circuit and a thermal accumulator in the secondary circuit using the refrigerants R744/CO2 are likewise known. One drawback in this context is the relatively high outlay on hardware, space and weight. In addition, only limited, low thermodynamics can be realized. Moreover, the efficiency is poor on account of the heat transfer from the refrigerant to the heat-transfer medium and from the heat-transfer medium to the useful air.
Engine-independent air-conditioning systems for long-haul commercial vehicles are also known. In this case, a thermal accumulator is loaded with refrigeration via a secondary circuit, with the associated drawbacks which have been mentioned above (hardware, space and weight), which means that this type of stationary air-conditioning is also somewhat unsuitable for use in passenger automobiles.